As illustrated in FIG. 1, a three-dimensional integrated photonic structure STR may conventionally comprise an electronic module 1, an integrated photonic module 2, a component for input/output of an optical signal, and a Ball Grid Array (BGA) substrate 3.
The electronic module 1 includes a plurality of integrated electronic circuits 10 and first solder balls 11 located on one of its faces. The integrated photonic module 2 includes a plurality of integrated photonic circuits produced, for example, in a semiconductor substrate 21, an interconnection part 22, first bonding pads 23 on its upper face, and second solder balls 24 on its lower face.
The component for input/output of an optical signal is not represented. The component may be, for example, a first optical fiber connected to the upper face of the photonic module 2 and optically coupled to the integrated photonic circuits produced in the semiconductor substrate 21.
The BGA substrate 3 includes third solder balls 30 on a first face and second bonding pads 33 on a second face opposite the first face. The substrate also includes metal lines and vias forming an interconnection network 31 making it possible to ensure electrical connection between the second bonding pads 33 and the solder balls 30.
The electronic module 1 may be electrically connected to the photonic module 2 by the first solder balls 11 and the first bonding pads 23. The photonic module 2 may be electrically connected to the BGA substrate 3 by the second solder balls 24 and the second bonding pads 33 located on the upper face of the substrate.
The photonic components of the photonic module are electrically connected to the BGA substrate by through-vias (TSV, Through Silicon Via) extending through the semiconductor substrate 21 of the photonic module, and by the second solder balls 24. The third solder balls 30 may, for example, be intended to be connected onto a printed circuit board.
In this type of three-dimensional integrated photonic structure, the component for input/output of an optical signal is connected to the upper face of the photonic module 2. The electronic module 1 and the integrated photonic module 2 are electrically connected to the BGA substrate 3 by through-vias 20 extending through the semiconductor substrate 21 of the photonic module 2. These through-vias 20 may generate mechanical stresses in the semiconductor substrate 21, which may then modify the refractive index of the medium over a certain distance around the vias.
For critical optical components, such as ring resonators, for example, the use of TSVs entails either specifying safety margins between a TSV and a critical optical component, which complicates the design of the circuits, or using TSVs with a small diameter, which complicates the fabrication of the circuits.